Method of rejuvenating a liquid hydrocarbon washing agent used in washing raw wool



July 17, 1956 A. G. BORCK 2,755,222

METHOD OF'REJUVENATING A LIQUID HYDROCARBON WASHING AGENT USED IN WASHING mwwoox. Filed May 24, 1951 ,wAsHm 2 PUMP 75R COOLER pg a M FAT AND WAX 3" ,2 HEAT/2f 1 l m nure/ e REM/NH? I; e a1 7 saunas 600m? 5 sm RA T01? I N VEN TOR. A/fred Gerhard Borck R IETHUD F REJUVENATHNG A LI QUID HYDRO- CARBQN WASHIIJG AGENT USED IN WASHING RAW WOOL Alfred Gerhard Borck, Tullinge, Sweden, assignor to Aktieholaget Separator, Stockholm, Sweden, a corporation of Sweden Application May 24, 1951, Serial No. 227,983

14 Claims. (Cl. 196-15) This invention relates to an improved method of washing wool with fluid hydrocarbons.

Raw wool has heretofore been washed in soap suds directly as it was obtained from the sheep. This has caused difliculties due to the wool fibre being hygroscopic. The wool fibre becomes felted during washing. The felt knots thus formed must be disentangled before spinning in the carding machines. Some of the fibres will then break, thus becoming shorter and less valuable. A substantial portion of these fibres falls away as loss. The carding cannot be carried out efficiently enough to remove all the knots, and so some of them will proceed to the spinning. Part of the interruptions in the looms is due to the resultirregularities of the spun thread.

It has therefore been suggested to use washing agents which do not cause the fibres to swell, for example, liquid hydrocarbons. As the washing from a practical point of view cannot be etfected with any great content of aromatic compounds in the hydrocarbons (the atmosphere in the locality would then become unsitable), it is necessary to use principally aliphatic hydrocarbons. Their power of dissolving the fats and waxes present in the wool is limited. Consequently, parts of the fats and waxes are precipitated, thus lowering the washing power of the solvents, and at the same time the precipitated particles are diflicult to separate from the solvents by continuous methods. However, due to the fact that solvents of the hydrocarbon type do not cause thefibres to become felted in the washing, it is very desirable to use them, the wool being of a considerably higher quality than wool washed in soap suds. It would be by far too expensive to substitute fresh solvent for the used solvent by means of a through-flow method. A continuous mechanical removal of the deposit or precipitates by a filter, or the like, is not practically feasible. Therefore, the use of hydrocarbons has not as yet been extensive in this particular industrial field.

According to the present invention, a system of washing machines and separators is used for purifying the wash liquid continuously, the liquid being caused to circulate through the system. Before the separation, the wash liquid is heated to a temperature sufliciently high to cause the deposit consisting of fats and waxes to be dissolved, whereupon the solvent is rapidly cooled down to a temperature which is suitable from a separating point of view. By such a temperature treatment of the wash liquid, the fats and Waxes can, however, be kept in a dissolved state for a limited period only, which means that the dirt must be removed during that period.

More specifically, the present invention resides in a method of washing raw wool with fluid hydrocarbons, characterized in that the washing agent consisting of hydrocarbons is circulated, at a temperature between room temperature and the flash point of the washing agent, through the washing machine and thence through a heating device, a device for rapid cooling of the washing agent, a mechanicalcleaning device for removing thereaired States Patent Q ice from the dirt extracted from the wool, and finally back to the Washing machine.

The washing agent discharged from the washing machine contains sludge which consists of the aforementioned dirt and also crystallized fats and waxes. The latter are in so finely divided a state that they cannot be separated from the washing agent by an ordinary separator. Therefore, according to a further feature of the invention, the washing agent is heated, after the washing, to such a temperature (e. g. higher than its flash point), and is kept for a sufiicient period at that temperature, that the fats and Waxes originating from the wool and which have not been dissolved at the washing temperature, are caused to dissolve.

As the equilibrium of dissolution of the fats and waxes in the washing agent does not occur immediately, upon a change of the temperature, it is possible, after the fats and waxes have been dissolved, to utilize this circumstance to bring about the removal of the dirt particles in thewashing agent mechanically, which is preferably done at a temperature below the flash point. The washing and also the mechanical cleaning are, in fact, not carried out in hermetically closed vessels, and for this reason none of these operations can take place at temperatures higher than the flash point. According to the invention, the washing agent is therefore cooled down so quickly, before entering the mechanical cleaning device, that the fats and waxes dissolved by the washing agent are not given the necessary time to precipitate to an appreciable extent during the mechanical cleaning. The cooling, as in the case of the heating after the washing machine operation, takes place under pressure in a closed system.

When the washing process takes place while the wash ing agent is circulated continuously, part of the washing agent coming from the mechanical cleaning device is withdrawn in order to be liberated from concentrated fats and waxes and is then led back to the washing machine. In this way, it is possible to always keep the concentration of fats and waxes in the washing agent fed to the washing machine, under a certain desired level.

The fats and waxes which precipitate after passing the washing agent through the mechanical cleaning device for the removal of the dirt, form such a fine sludge that if it is to be separated wholly or largely in a centrifugal separator, this must be done in such a separator having shock-free liquid feed, e. g., a separator of the hermetically closed type. In order to make it possible to recover the desired quantity of fats and waxes in this centrifugal separation, the latter should be preceded by a cooling of the washing agent to a temperature equal to or below the washing temperature.

After cooling the washing agent rapidly to about 40 C., the fats and waxes can be kept dissolved at this temperature for 2 or 3 minutes, so that it is possible to separate out the dirt quite unhindered, e. g., by centrifugal separation, as mentioned above. This means that the fat-and-wax content in the washing agent may be allowed to rise to the value which is limited by the necessary Washing effect in the washing machine.

If the above-mentioned heating of the washing agent should be omitted, the dirt discharged through the peripheral nozzles of the centrifugal. separator would contain only about 10% of real dirt. This means a loss of about consisting of Washing agent including fat and wax. On the other hand, if, according to the present invention, the washing agent is first heated and then quickly cooled down, the dirt in the centrifugal separator will behave as if there were no fats or waxes, the effect being that the concentration of real dirt at the separator nozzles will rise to about 45%, thereby reducing the loss to 55% only.

When separating fats and waxes from the Washing agent, the temperature and the time available for the crystallization of the fats and waxes determine the quantity of fats and waxes which can be removed in this way. To remove them completely requires relatively low temperatures, as to minus 10 C., which renders the process less economical as compared with the distilling process. Therefore, it is possible, according to the invention, to use in practice, for the removal of fats and waxes from the washing agent, a combined process of centrifugal separation and distillation. This is done in such a way that the washing agent, after having been rid of dirt by separators, is cooled down to a temperature which can be obtained by cooling with ordinary tap water, whose temperature is as a rule 8 to 10 C. The washing agent is thus cooled down to a temperature be tween 40 and 10 C., for example. The precipitated fats and waxes are then removed from the washing agent in a centrifugal separator with shock-free feed. After this separation, the heating agent is again heated to the Wash ing temperature, and part of the washing agent is conveyed to a distilling device by which the portion of fats and waxes still present in a dissolved state is extracted. In this way, the necessary capacity of the distilling device can be reduced to 0.5 kg. of distilled washing agent (or less) per kg. of washed raw wool, as a considerable part of the fats and waxes have already been recovered by centrifugal separation.

According to a modification of the invention, the fats and waxes can be separated from the washing agent by treating them, after passing through the mechanical cleaning device, directly in a distilling device. Thus, both dissolved and precipitated fats and waxes are separated off.

In the accompanying drawing, the single illustration is a schematic view of a system for use in practicing the invention. This system comprises a washing machine 1, a pump 2 for circulating the washing agent through the whole system, a heating device or zone 3 in which fatandwax sludge in the washing agent coming from the washing machine 1 is caused to dissolve, a heat retainer or holding zone 4 which keeps the washing agent at its previously heated temperature for a period sufficient for the remaining fats and waxes to dissolve, a device 5 for rapid cooling of the washing agent, and a separator 6, such as a centrifugal separator, for separating dirt particles mechanically from the washing agent, these dirt particles being removed as sludge from the separator 6, as indicated by the arrow 6a. The washing agent from the dirt separator 6 is circulated back to the washing ma chine 1 through the return line 9.

When circulating the washing agent continuously, part of it is withdrawn from separator 6 and led to a device 7 for separating fats and waxes, as by centrifugal separation or distilling, so that the fat and wax quantity is always kept below a certain level. By further cooling of the washing agent in a cooler 8 interposed between the separators 6 and 7, it is possible to increase the quantity of precipitated fats and waxes and, therefore, the quantity of fats and waxes separated by separator 7. Then, the washing agent is led back to the washing machine 1, by way of return pipes 9a and 9. The separated fat and wax are removed from the separating device 7 as shown at 7a, and are utilized for different purposes.

The invention is further explained by the following example:

As the wool washing agent, a liquid aliphatic hydrocarbon is used, which has a content of aromatic compounds of 5 to 10% by weight. Its flash point is about ii-48 C. The washing agent is introduced into the washing machine 1 at a temperature of 3035 C. After the washing, the washing agent is heated at 3 to about 70l20 C. and is then maintained at this temperature in the holding zone 4 for a period which is a function of the heating temperature and is long enough so that fats and waxes are dissolved. Generally, a holding period 4 of 15-20 minutes is sufficient when the holding temperature is 70-120 C.

The cooling at 5 should take place with the greatest possible difference in temperature between the washing agent and the cooling medium. The cooler 5 may be a plate type of heat exchanger. The total cooling time, including the time of passage through the mechanical cleaning device 6, is preferably between 1 and 3 minutes and should not exceed 15 to 30 minutes. After 30 minutes, the washing agent will be in about the same condition as when it left the washing machine, before being heated.

The process as described so far allows repeated use of the washing agent but does not provide an entirely con tinuous operation, since no provision is made for keeping the concentration of fats and waxes below a certain level. If a continuous process is to be used, these substances must be removed, which can be done by gravity separation, or centrifugal separation, e. g., in an hermetically closed separator, as mentioned above. This will then separate off the undissolved fats and waxes. There is a definite relation between the capacity of the fat-and-wax separator and the quantity of fats and waxes which have been added in the washing system by the wool. The quantity of separated fats and waxes can be raised by reducing the separating temperature at 7, whereby larger quantities of fats and waxes are precipitated and can be separated off. Distillation can also be used at 7 for removing fats and waxes from the washing agent. The distillation apparatus should be dimensioned so that 1 to 1.5 kg. of washing agent is distilled per kg. of raw wool fed into the washing system. As distillation is very expensive, a combination of centrifugal separation and distillation is desirable, as it is then possible to keep the quantity to be distilled between 0.5 and 1.0 kg. per kg. of raw wool.

The dirty sludge obtained at 6a from the separator 6, and which contains a portion of the washing agent, causes trouble when it is desired to dispose of it. It cannot be simply discharged, as into a watercourse near the wool washing plant, because the sludge is strongly contaminated by the washing agent itself. Furthermore, burning the sludge will cause difficulties, as with the burner nozzles, not to mention the loss of washing agent and wool grease contained in the sludge.

These difficulties are avoided by a further feature of the present invention. Specifically, the dirt extracted from the wool by the Washing agent is removed from the latter in a centrifugal bowl into which water or a water solution is introduced so that a layer of water or water solution is formed at the periphery of the centrifugal bowl, through which the dirt particles pass on their way to the periphery of the bowl. In this way, the dirt particles are substantially de-oiled, since the dirt can pass more readily through the water layer than can the oil.

For this purpose, it is possible to use centrifuges of different types suitable for the separation of sludge, e. g., a clarifier type centrifuge where the sludge is accumulated at the bowl Wall, or a centrifuge having provision for continuous flushing of the sludge through an outlet co-axial with the centrifuge spindle. Preferably, a centrifuge is used with nozzles at the periphery of the centrifugal bowl, through which the dirt is discharged in the form of sludge containing some of the water or water solution.

The water or the water solution can be introduced with the washing agent into the centrifuge 6 through the same inlet. In this case, however, the dirt particles will have substantially the same flow path as the drops of water or water solution, so that the difference in speed of flow between these drops and the dirt particles will be relatively small. The de-oiling effect on the dirt particles will not, therefore, be as good as possible. The de-oiling effect can be considerably increased if the water or the Water solution is introduced separately into the centrifuge, as through a feed line 6b. When using a nozzle type of centrifuge, the water or water solution can be fed into the bowl close to the nozzles at the periphery of the bowl, as by the arrangement disclosed in Strezynski Patent No. 2,518,436 of August 8, 1950. The dirt particles are then de-oiled more effectively, especially if they meet a counter-current of water or water solution moving partly inward toward the bowl axis, which is the case if the water or water solution is fed into the centrifuge at a rate in excess of the rate at which it discharges with the dirt sludge through the nozzles. In this case, the surplus quantity of water or water solution may be discharged over the usual regulating disc, so that the desired boundary level between the washing agent on the one hand and the water or water solution on the other hand can be maintained.

As the dirt particles in the wool are often comparatively large, e. g., measuring about one millimeter in diameter (grains of said or the like), the centrifuge nozzles must have a suificiently large inner diameter to pass the largest dirt particles. This means that comparatively large quantities of water or water solution go with the dirt sludge through the nozzles, so that the sludge has a low concentration of dirt particles. This is of minor importance in such cases where the wool washery has an ample supply of water. If this is not the case, part of the dirt sludge discharged from the centrifuge may be led back to the centrifuge through a separate inlet and passage leading to the vicinity of the nozzles arranged at the periphery of the centrifugal bowl, and the water or water solution may be led to a point between the sludge layer and the washing agent layer in the bowl so as to form between these layers a layer of water or water solution. It is particularly desirable in this case, as well, that the water or water solution be added in excess and that the water or water solution be led back, wholly or partly, from its outlet from the centrifuge to its inlet in the centrifuge. In this way, it is possible to increase considerably the concentration of dirt particles in the sludge discharged from the centrifuge, and it is necessary to feed into the centrifuge only small quantities of water or water solution to replace that lost with the sludge. The de-oiling effect of the water or Water solution is considerably improved by raising its temperature to 50 to 70 C., for instance, which also causes any wool grease left on the dirt particles to dissolve or melt in the boundary layer between the washing agent and the water or water solution. It is also possible to increase the de-oiling power of the water or water solution by adding certain agents, such as surface tension reducing agents.

In order to prevent the washing agent from forming emulsions with subsequent loss of this agent, the water solution which is used may be a solution of an electrolyte, e. g., a common salt solution.

If the difference in speed between the water or water solution and the dirt particles in the centrifugal bowl, in the radial direction towards the nozzles, is too small (as in the case when using nozzles with a large inner diameter), the de-oiling effect will be bad, and if the difference in speed in the vertical direction between the washing agent and the Water or water solution is too great (as for instance in the case of great excess of water or Water solution), there will be a formation of emulsion. Therefore, the different speeds of both liquids should be so regulated (as by conventional controls) that good de-oiling but no formation of emulsion is obtained. In the case of a slight excess of water or water solution, the risk of emulsification will thus be small but the de-oiling effect bad, and with great excess of water or water solution the condition will be reversed. If this speed adjustment should not be suflicient in itself, the desired effect can be obtained by the aforementioned steps for promoting de-oiling and preventing emulsification.

Referring back to the system as illustrated in the drawing, the heating, holding and cooling at 3, 4 and 5, respectively, are preferably effected in a closed system under super-atmospheric pressure. The cooler 8 prefera- '6 bly cools the washing agent from the cleaning opera tion 6 to a temperature of 1040 C.

I claim:

1. A method of rejuvenating a liquid hydrocarbon washing agent used in the washing of raw wool and containing a sludge consisting of fats and waxes acquired by passing the liquid agent through the wool washing operation at atmospheric pressure and at a temperature between room temperature and the flash point of the washing agent, which comprises passing said liquid agent from the washing operation through a heating Zone under super-atmospheric pressure and therein heating said agent to a temperature higher than its flash point and sufiicient to dissolve the fats and waxes of the sludge, then rapidly cooling the heated agent under super-atmospheric pressure to a temperature substantially below its flash point to product an under-cooled solution of the fats and Waxes in the Washing. agent, and separating the dirt extracted from the wool from the agent before the fats and waxes crystallize out appreciably from the agent.

2. A method according to claim 1, in which the washing agent is maintained at about the temperature to which it is heated in said zone, for a period sufiicient to dissolve, prior to said cooling, the fats and waxes originating from the wool and not dissolved at the washing temperature.

3. A method according to claim 1, comprising also removing concentrated fats and waxes from at least part of the Washing agent discharged from the dirt separatingoperation.

4. A method according to claim 1, comprising also removing concentrated fats and waxes from at least part of the washing agent discharged from the dirt separating operation, said removing being effected by feeding the agent under substantially air-tight conditions to a centrifugal separating operation and there separating undissolved fats and waxes while excluding air from the centrifugal operation.

5. A method according to claim 1, comprising also removing concentrated fats and waxes from at least part of the washing agent discharged from the dirt separating operation, said removing being effected by cooling the washing agent from the dirt separating operation, to precipitate fats and waxes therein, and then centrifuging the agent to remove at least part of the undissolved fats and waxes.

6. A method according to claim 1, comprising also removing concentrated fats and waxes from at least part of the washing agent discharged from the dirt separating operation, said removing being effected by cooling the washing agent from the dirt separating operation to a temperature of 10 to 40 C., to precipitate fats and waxes therein, and then centrifuging the agent to remove at least part of the undissolved fats and waxes.

7. A method according to claim 1, comprising also removing concentrated fats and waxes from at least part of the washing agent discharged from the dirt separating operation, said removing being effected by cooling the washing agent from the dirt separating operation, to precipitate fats and waxes therein, then centrifuging the agent to remove at least part of the undissolved fats and waxes, and then distilling the washing agent to remove remaining fats and waxes.

8. A method according to claim 1, comprising also removing concentrated fats and waxes from at least part of the washing agent discharged from the dirt separating operation, said removing including distillation of the washing agent.

9. A method of rejuvenating a liquid hydrocarbon washing agent used in the washing of raw wool and containing a sludge consisting of fats and Waxes acquired by passing the liquid agent through the wool washing operation at atmospheric pressure and at a temperature between room temperature and the flash point of the washing agent, which comprises passing said liquid agent from the washing operation through a heating Zone under super-atmospheric pressure and therein heating said agent to a temperature higher than its flash point and sufiicient to dissolve the fats and waxes of the sludge, then rapidly cooling the heated agent under super-atmospheric pressure to a temperature substantially below its flash point to produce an under-cooled solution of the fats and waxes in the washing agent, centrifugally separating the cooled agent in the presence of a Water layer outside the body of washing agent, whereby the dirt separated from the agent is substantially de-oiled in passing through the water layer to the periphery of the centrifugal locus, said centrifugal separating operation being completed before the fats and waxes crystallize out appreciably from the agent, and separately discharging the washing agent from the centrifugal separating operation.

10. A method according to claim 9, comprising also the step of feeding water into the centrifugal separating operation together with the washing agent, to form said water layer.

11. A method according to claim 9, comprising also the step of feeding water into the centrifugal separating operation separately from the washing agent, to form said water layer.

12. A method according to claim 9, in which the dirt is discharged through the outer periphery of the centrifugal locus, and comprising the step of feeding water, separately from said agent, to said layer and the dirt discharge region at the outer periphery of said locus, said discharge dirt and some of the water being returned at least in part as sludge to said dirt discharge region, separately from said agent and said first water feed, said first water feed being delivered to the centrifugal locus at a point between the returned sludge and the body of washing agent, said water being fed to said region at a rate in excess of the rate at which the water is discharged with the dirt, the excess water being discharged separately from the locus.

13. A method according to claim 9, in which the dirt is discharged through the outer periphery of the centrifugal locus, and comprising the step of feeding water separately from said agent, to said layer and the dirt discharge region at the outer periphery of said locus, said water being fed to said region at a rate in excess of the rate at which the water is discharged with the dirt, the excess water being discharged separately from the locus.

14. A method according to claim 9, in which the dirt is discharged through the outer periphery of the centrifugal locus, and comprising the step of feeding water separately from said agent, to said layer and the dirt discharge region at the outer periphery of said locus, said water being fed to said region at a rate in excess of the rate at which the water is discharged with the dirt, the excess water being discharged separately from the locus and returned at least in part with said water fed to the locus.

References Cited in the file of this patent UNITED STATES PATENTS 548,942 Wingfield Oct. 29, 1895 549,041 Wingfield Oct. 29, 1895 796,530 Quackenbos Aug. 8, 1905 1,351,047 Leitch Aug. 31, 1920 1,525,016 Weir Feb. 3, 1925 2,518,436 Strezynski Aug. 8, 1950 

1. A METHOD OF REJUVENATING A LIQUID HYDROCARBON WASHING AGENT USED IN THE WASHING OF RAW WOOL AND CONTAINING A SLUDGE CONSISTING OF FATS AND WAXES ACQUIRED BY PASSING THE LIQUID AGENT THROUGH THE WOOL WASHING OPERATION AT ATMOSPHERIC PRESSURE AND AT A TEMPERATURE BETWEEN ROOM TEMPERATURE AND THE FLASH POINT OF THE WASHING AGENT, WHICH COMPRISES PASSING SAID LIQUID AGENT FROM THE WASHING OPERATION THROUGH A HEATING ZONE UNDER SUPER-ATMOSPHERIC PRESSURE AND THEREIN HEATING SAID AGENT TO A TEMPERATURE HIGHER THAN ITS FLASH POINT AND SUFFICIENT TO DISSOLVE THE FATS AND WAXES OF THE SLUDGE, THEN RAPIDLY COOLING THE HEATED AGENT UNDER SUPER-ATMOSPHERIC PRESSURE TO A TEMPERATURE SUBSTANTIALLY BELOW ITS FLASH POINT TO PRODUCT AN UNDER-COOLED SOLUTION OF THE FATS AND WAXES IN THE WASHING AGENT, AND SEPARATING THE DIRT EXTRACTED FROM THE WOOL FROM THE AGENT BEFORE THE FATS AND WAXES CRYSTALLIZE OUT APPRECIABLY FROM THE AGENT. 